1. Field of the Invention
The present invention relates generally to an apparatus for ground water testing. More specifically, the present invention relates to a cone tipped cylindrical probe or piezocone which is used as an effective means of pore pressure measurements which can be converted into values for water table evaluation for accessing environmental site conditions.
2. Description of the Prior Art
The cone penetration test was originally developed to measure in-situ soil properties for the design of deep foundations. The electric version of the cone penetration test was introduced commercially in the nineteen seventies primarily as a geotechnical exploration tool. More recently, the cone penetration test range of applications has been extended to environmental site investigations.
The electric cone penetration test is currently being used as an effective means of hydrogeologic site characterization and subsurface plume tracking. An electric cone penetration test probe or piezocone measures pore water pressure and soil resistance to penetration while being advanced into the ground by an approximately 20-ton hydraulic cone penetrometer rig.
Computer processing of the piezocone measurements generally provides detailed stratigraphic profiles which depict depths of water bearing formations and variations in permeability. This data may then be used to determine the optimum depths at which to conduct ground water sampling for plume delineation; to determine direction and gradient of subsurface water flow; to check for aquifer communication and for monitoring of remediation efforts.
The piezocone has several advantages over conventional cone penetration testing methods and apparatus including: (1) the ability to distinguish between drained, partially drained and undrained soils; (2) the ability to correct measured cone data to account for unbalanced water forces due to unequal end areas in cone design; (3) the ability to evaluate flow and consolidation characteristics; (4) the ability to assess equilibrium groundwater conditions; (5) improved soil profiling and identification; and (6) improved evaluation of geotechnical parameters.
While there are a number of commercially available piezocones which may be used for hydrogeologic site characterization and subsurface plume tracking there is a need for a piezocone which will provide very accurate pore pressure measurements. In particular, the piezocone should be able to provide precise values of pore pressure having a total error of less than 0.9 inches of water.